Shias (mostly in South-Asian countries) make replicas of taboot (biet), zari, zuljana and a'lam (Islamic flag) during Muharram processions.
From where has this practice started and is it allowed in ...

I came across to this video.
Imam and people around him are flogging themselves. Why?
What does this mean in Islam? any hadith or Quran to back this up?
PS: I am not being funny or insulting anyone....